1. Field of the Invention
The present invention relates electron beam apparatus having an energy analyzer or energy analyzers for analyzing electron beam energy such as an electron beam energy loss spectrum measuring apparatus or an Auger electron spectrum measuring apparatus.
2. Description of the Related Art
In recent years, the importance of analyzing composition, state of electrons, structure, etc., of a fine region on a sample surface has been increased in developments and researches of the electronic materials such as semiconductors or newly developed materials such as fine ceramics. For this reason, apparatus are used for analyzing a fine region of the order of microns by irradiating a narrow focused electron beam onto the sample.
An example of this type of electron beam apparatus is shown in FIG. 5. In this figure, numeral 1 denotes an electron gun and numeral 2 denotes an electron lens, both being accommodated in an electron-optical lens column 3. The other components includes: an electron beam (EB) 4; a sample 5; an energy analyzer 6; a focusing lens 7; sector electrodes 8; an electron beam detector 9; a signal amplifier 10; a computer 11; an input device 12; a display unit 13; and a storage unit 14.
In such an apparatus, the electron beam 4 emitted from the electron gun 1 is irradiated onto the sample 5 as it is focused by the electron lens 2. As a result, reflected electrons or electrons generated due to the electron beam irradiation are emitted from the sample 5, the emitted electrons being guided to the energy analyzer 6. At the energy analyzer 6, the energy axis is moved in accordance with a command from the computer 11 to perform energy analysis of the guided electrons. The result of energy analysis detected at the electron beam detector or detectors 9 is/are for example displayed on the electron display unit 13 through a predetermined signal processing. It should be noted that, in such an apparatus, the focusing lens 7 is provided at the energy analyzer 6 so that electrons from a region of several hundred .mu.m to 1 mm of the sample may be efficiently guided into the energy analyzer 6 in order to analyze a fine region of the sample.
Here, a problem which must be considered in performing analysis of a fine region of the sample by an irradiation of such electron beam is that matching of three regions assumed on the sample surface is desirable to perform a suitable analysis, the three regions being an analytical target area, an electron beam irradiation position at the time of analysis and an energy analysis area. In other words, it is necessary for a suitable analyzing operation to accurately irradiate the electron beam onto an intended position of the analysis and to efficiently take in by the energy analyzer the electrons emitted from the sample due to the electron beam irradiation. Here, the analytical target area refers to a region on the sample surface which is considered as the object of analysis by the analyst; the analyzing electron beam irradiation position refers to the position on the sample surface onto which the electron beam emitting from the electron-optical lens column is irradiated when the electron beam apparatus is in its state for executing analysis; and the energy analysis area refers to the region where the electrons emitted from the sample are efficiently guided to the energy analyzer.
For this reason, in the conventional electron beam apparatus, the electron-optical lens column, energy analyzer, and vacuum vessel for forming an analytical chamber, etc., are manufactured highly accurately in their dimension to make smaller the errors in mechanically attaching for example the electron-optical lens column and the energy analyzer to the vacuum vessel. In addition, it is usually constructed so as to allow an adjustment of relative position or posture of the respective portions of the apparatus such as the electron gun, a stage for placing a sample and the energy analyzer. For example, means capable of a fine adjustment of the relative position is generally provided to enhance the degree of matching of the above described regions. Known fine adjustment means of this type include: adjustment means for, while observing an electron beam detection signal from the energy analyzer in a state where the electron beam apparatus is operated, adjusting the positions, for example, of the electron-optical lens column, energy analyzer and sample or adjusting the analyzing electron beam irradiation position by an electron beam alignment device provided on the electron-optical lens column such that the detection signal is brought to its maximum in order to match the analyzing electron beam irradiation position and the energy analysis area.
In the conventional apparatus as described above, however, the two regions, i.e., the analyzing electron beam irradiation position and the energy analysis area cannot be detected with a clear distinction from each other. In actual operation, a manual adjustment by the operator is required, resulting in an intricate and time consuming adjustment.
Further, in the case where an extremely limited region is to be measured, matching is desired not only between the analyzing electron-beam irradiation position and the energy analysis area but also of the three regions also including the analytical target area. A suitable method for this has not been provided.
As described above, fine adjustment means for matching an analyzing electron beam irradiation position and an energy analysis area which is conventionally employed in an electron beam apparatus having an energy analyzer or energy analyzers requires an intricate and time consuming adjustment as it is incapable of providing a view with a clear distinction between the two regions. Further, a suitable method or means has not been provided to match the three regions, i.e., analytical target area, analyzing electron beam irradiation position and energy analysis area. In view of these current state of facts, the present inventor undertook an intensive research and has achieved the present invention.